How Rooibos Is Processed

Rooibos processing is the ordered chain of work that stands between a cut branch of the red bush and a finished product you can put in a cup, a teabag, or a bottled drink. It covers everything the plant undergoes after it leaves the field: the cut, the bruising, the heaped rest that the trade calls fermentation, the long open-air dry, the sieving and grading that sort one harvest into many products, the heat step that makes the leaf safe to ship, the vigilance that keeps a lookalike weed out of the batch, and the separate industrial path that ends in a soluble powder rather than a leaf. Almost all of it is the plant's own compounds reacting with air, water, heat and time, under supervision, rather than any chemistry added from outside.

Seven stages carry a branch from field to finished product, in the order the leaf actually meets them. Cutting the harvest covers the branch cut and the rotary cutter, and the bruising that everything downstream depends on. The fermentation heap covers the temperature window and the overnight turning. Drying covers the dawn resumption and the moisture target that makes the tea storable. Grading and cut size covers the sieves, the four quality tiers, and the three cut sizes that decide how your cup behaves. Food safety covers steam pasteurisation, what it reliably does, and the one organism the field itself says is not yet fully understood. Keeping contamination out covers bitterbos, the lookalike weed identified as the major source of documented alkaloid contamination. Rooibos as extract covers the different path taken by sieve dust and purpose-grown leaf.

Cutting the harvest

Rooibos is harvested once a year, from summer into early autumn, and the cut is deliberately high. Whole branches are taken about 50 centimetres above the ground¹ (roughly 20 inches), which leaves the bush enough standing frame to regrow for the following season. It is a single annual window for the whole country's cup: South Africa produces more than 20,000 tonnes of rooibos a year¹ (roughly 22,000 US tons) from the Cederberg and its neighbouring districts, centred on Clanwilliam.

At the yard, the sheaves go through a rotary cutter, which chops branch, leaf and stem together into uniform lengths of 1.5 to 5 millimetres², with the blades resharpened roughly hourly to hold that consistency. Size is only the visible result. The same blades also bruise the plant, cracking its cell walls so the compounds held inside can meet the air. This bruising is not incidental damage to be minimised. It is the step that makes everything after it possible, and a batch that is cut cleanly but not bruised has nowhere to go. The full sequence of yard operations, cut through heap through dry, is set out in the Ministry's account of how the harvest is processed.

The machinery arrived late and by an odd route. Cutting was once done by hand with an axe and a wooden mallet, the moker, then by an adapted chaff-cutter borrowed from black tea processing, and from 1954 to 1993 the state Rooibos Tea Control Board ran the only legal cutting operation in the country. The rotary cutter is the industry standard, and the longer story of how it got there is told in the history of rooibos cutting.

The fermentation heap

The trade calls this step fermentation out of long habit, and the habit is worth naming plainly: no yeast and no bacteria are doing the work. What happens in the heap is oxidation, driven by the plant's own enzymes now that the bruising has let air in. The word stuck, so the Ministry uses it, with the caveat attached.

The cut, bruised leaf is spread in the open drying yards, watered, and left in heaps to sweat. Watering typically begins in mid-afternoon³, after which the heaps are turned and aired several times before evening and then roughly every four hours through the night. That round-the-clock attention is for the temperature window, which is so narrow that a slip of only a few degrees can ruin the batch. The heap must hold between 34 and 42 degrees Celsius³ (about 93 to 108 Fahrenheit), with 38C treated as the target, for roughly 15 hours³. Run below about 34C and the batch turns bitter. Run above about 42C and the flavour goes bland and flat. That narrow window is why a Cederberg yard keeps someone checking the heap through the small hours rather than closing up for the evening.

Drying

Work resumes around dawn. The fermented rooibos, deep amber now rather than green, is pressed, traditionally by driving a tractor over the rows, so its own coloured liquid runs back through the pile³, then spread thin across the yard to dry in the open Cederberg sun. Workers reposition it through the day as the surface dries unevenly. Drying runs about nine hours³ and is judged finished once moisture content drops below roughly 8.5 percent, dry enough that the tea keeps in storage and survives shipping without spoiling. A tin bought months later owes that shelf life to a yard's judgement about a single morning's sun.

Grading and cut size

Once dry, one harvest becomes many products. The South African Rooibos Council states that rooibos is graded on colour, flavour, cut length and aroma⁴, and the sorting that makes those judgements possible is mechanical: the dried leaf passes through a bank of sieves, rolling, vibrating, maxi and indent types², separating the batch by size and quality, with a single facility able to sieve twenty tons in a day.

What comes out is sorted into four quality tiers⁷:

Cut size is a separate decision from quality, and it is the one you taste most directly. A finer cut exposes more surface area to hot water, so more compounds extract faster and the cup reads as stronger and more intense. A coarser cut releases more slowly and evenly, and reads as rounder and calmer. Three cut grades carry most of the trade:

Nothing is wasted at the fine end. What sieves out as the very finest material becomes rooibos powder and micro powder⁵, sold for espresso-style blends, instant granulates, smoothies and baking rather than steeped as loose leaf. The tier and cut a batch lands in, and what that means for a buyer, is covered in full in the Ministry's guide to grading and cuts.

Graders do not work from private impressions alone. Researchers at the Agricultural Research Council's Infruitec-Nietvoorbij campus and Stellenbosch University's Department of Food Science built a rooibos sensory wheel⁸ from tasting-panel data, first developed in 2011 and revised in 2017 and 2021, which gives graders, producers, importers and flavour houses a shared vocabulary for the tea's flavours and mouthfeel. The food scientist Elizabeth "Lizette" Joubert was on the founding team and has kept teaching graders to use it⁹.

Food safety: pasteurisation and its limits

After grading and sieving, every batch goes through steam pasteurisation, exposed to steam at around 160 degrees Celsius² (320 Fahrenheit) for at least 90 seconds, then screened directly for Salmonella, E. coli and other microbes at facilities holding FSSC22000 and ISO 9001 food-safety certification¹⁰. It is a real and tested safeguard, needed precisely because the leaf ferments and dries outdoors on bare ground rather than under cover.

The safeguard is real, and it is not the whole story, and the Ministry would rather say so than let a tin's silence do the reassuring. A 2014 peer-reviewed review by food scientists at Stellenbosch University and the University of the Western Cape found that rooibos "naturally contains a high microbial load,"¹¹ and that "the presence of Salmonella in Rooibos is poorly understood," a gap the review itself called on the industry to close. A single 2013 recall of a Canadian rooibos blend for possible Salmonella, and a 2022 laboratory study confirming that a proper full boil (not a lukewarm cup) destroys the bacteria far more reliably than a lighter brew, are both set out in full in pasteurisation and Salmonella safety. The short version: the certified heat step and a kettle brought properly to the boil are two safeguards, not one, and between them they close a gap the field itself is still working on.

Keeping contamination out: the bitterbos weed

Rooibos makes none of the liver-toxin family called pyrrolizidine alkaloids on its own. Chemists have traced the major source of every contaminated batch they examined¹² to a Cape weed, Senecio angustifolius, known as bitterbos, which resembles rooibos closely enough, flower colour included, to be cut and dried along with the harvest by mistake. Control is a field and sorting problem, not a problem with the bush itself, and it is why the EU now sets rooibos its own, higher pyrrolizidine ceiling¹³ rather than judging it against the general herbal-tea limit. On the more familiar worry of pesticide spray, the record is plainer good news: a 2022 South African study screening 100 retail rooibos products¹⁴ found only one with any detectable trace at all, well under safety limits. The weed, its identification, and how a yard keeps it out are covered in full in the lookalike weed problem.

Rooibos as extract: a different path

Not all processed rooibos ends as leaf. Extract is a separate product, made by soaking purified leaf and stem in hot water, filtering out the solids, concentrating what remains, and spray-drying it¹⁵ into a fine, water-soluble powder, its raw material a mix of purpose-grown leaf and the industrial-grade material, the finest sieve dust from grading, too fine to steep loose without grit, from earlier in this page's own tier table. It comes in red, from fermented and oxidised leaf, and green, dried quickly to skip oxidation and marketed for higher retained aspalathin, which is the same divide the leaf itself has and is set out in green versus red rooibos. From there it goes into flavoured water, energy drinks, baked goods, dairy, sauces, anti-ageing creams, soothing balms and supplement capsules.

One difference matters more than the rest. Whole leaf is patient: stored dry and out of heat, it keeps. Extract powder is fragile. A 2021 Stellenbosch study found that spray-dried green rooibos iced-tea powder formulations lost between roughly 9.7 percent and 90.3 percent of their aspalathin over twelve months at 40 Celsius¹⁶ (104F), depending on packaging and formulation, so both heat and packaging mattered a great deal. That range is precisely why processors reach for encapsulation techniques to protect the molecule, and the engineering behind that is given in full in how rooibos becomes an extract.

Reading a tin with this in mind

A Superior-grade whole needle and an Industrial-grade fragment bound for an extract vat come from the same bush, the same heap, and the same Cederberg sun. What separates them is which sieve they fell through and which order they were sorted in, not any difference in how carefully they were grown. So the next time a tin promises Superior grade, or a teabag brews darker than the loose leaf in your cupboard, you now know the yard behind that difference: a branch cut high enough to regrow, a night spent within a few careful degrees, a morning of open-air sun, and a grader's eye doing the rest.